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Back in the Old Days…
Back in the Old Days…
Back in the Old Days…
Back in the Old Days…
Back in the Old Days…
Back in the Old Days…
Back in the Old Days…
Back in the Old Days…
Packet Switching (Internet)
Packet Switching (Internet)
Packet Switching (Internet)
Packet Switching (Internet)
Packet Switching (Internet)
Packet Switching (Internet)
Packet Switching (Internet)
Packet Switching (Internet)
Third Step: How To Find Nodes
Third Step: How To Find Nodes
Domain Name System
Domain Name System
Картинки из презентации «15-744: Computer Networking» к уроку английского языка на тему «Тексты на английском»

Автор: Srinivasan Seshan. Чтобы познакомиться с картинкой полного размера, нажмите на её эскиз. Чтобы можно было использовать все картинки для урока английского языка, скачайте бесплатно презентацию «15-744: Computer Networking.ppt» со всеми картинками в zip-архиве размером 354 КБ.

15-744: Computer Networking

содержание презентации «15-744: Computer Networking.ppt»
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115-744: Computer Networking. L-1 Intro 28ARP maps IP addresses to Ethernet
to Computer Networks. addresses Local, works only on a
2Outline. Administrivia Whirlwind tour particular network Routing protocol
of networking. © Srinivasan Seshan, 2002. provides path through an internetwork. ©
L -1; 9-11-02. 2. Srinivasan Seshan, 2002. L -1; 9-11-02.
3Who’s Who? Professor: Srinivasan 28.
Seshan http://www.cs.cmu.edu/~srini 29Network:Address Resolution Protocol.
srini@cmu.edu Office hours: Wed Broadcast: who knows the Ethernet address
1:30-2:30pm TA: Amit Manjhi for Ethernet. Unicast: Yes,
manjhi@cs.cmu.edu Office hours: Mon it is 08-00-2c-19-dc-45. Ethernet. ©
3:00-4:00pm Course info Srinivasan Seshan, 2002. L -1; 9-11-02.
http://www.cs.cmu.edu/~srini/15-744/F02/. 29.
© Srinivasan Seshan, 2002. L -1; 9-11-02. 30Internetwork: Datagram Routing. H:
3. Hosts R: Routers. H. H. H. H. H. Routers
4Objectives. Understand the send packet to next closest point. R. R.
state-of-the-art in network protocols, R. R. R. R. R. R. © Srinivasan Seshan,
architectures and applications Understand 2002. L -1; 9-11-02. 30.
how networking research is done Teach the 31Routing. Forwarding tables at each
typical constraints and thought process router populated by routing protocols.
for networked systems How is class Original Internet: manually updated
different from undergraduate networking Routing protocols update tables based on
(15-441) Training network programmers vs. “cost” Exchange tables with neighbors or
training network researchers. © Srinivasan everyone Use neighbor leading to shortest
Seshan, 2002. L -1; 9-11-02. 4. path. © Srinivasan Seshan, 2002. L -1;
5Web Page. Check regularly!! Course 9-11-02. 31.
schedule Reading list Lecture notes 32Fourth Step: Application Demands.
Announcements Assignments Project ideas Reliability Corruption Lost packets Flow
Exams Student list. © Srinivasan Seshan, and congestion control Fragmentation
2002. L -1; 9-11-02. 5. In-order delivery Etc… © Srinivasan
6Course Materials. Research papers Seshan, 2002. L -1; 9-11-02. 32.
Links to ps or pdf on Web page Combination 33X. What if the Data gets Corrupted?
of classic and recent work ~40 papers Problem: Data Corruption. GET index.html.
Optional readings Recommended textbook For GET windex.html. Internet. Solution: Add a
students not familiar with networking checksum. 0,9. 9. 6,7,8. 21. 4,5. 7.
Peterson & Davie 2nd edition 2 copies 1,2,3. 6. © Srinivasan Seshan, 2002. L -1;
on reserve Kurose & Ross (preferably 9-11-02. 33.
2nd edition) I have some spare (1st ed) 34What if Network is Overloaded?
that I can lend out. © Srinivasan Seshan, Problem: Network Overload. Solution:
2002. L -1; 9-11-02. 6. Buffering and Congestion Control. Short
7Grading. Homework assignments Problem bursts: buffer What if buffer overflows?
sets & hands-on assignments (15%) Packets dropped Sender adjusts rate until
Hand-ins for readings (10%) Class load = resources Called “congestion
participation (5%) 2 person project (30%) control”. © Srinivasan Seshan, 2002. L -1;
Midterm exam (20%) Final (2nd Midterm) 9-11-02. 34.
exam (not cumulative) (20%). © Srinivasan 35What if the Data gets Lost? Problem:
Seshan, 2002. L -1; 9-11-02. 7. Lost Data. GET index.html. Internet.
8Waitlist & HW 0. HW 0 – due next Solution: Timeout and Retransmit. GET
Thursday in class If you are trying to add index.html. GET index.html. Internet. GET
class HW 0 is due on Tuesday in class I index.html. © Srinivasan Seshan, 2002. L
will email enrollment decisions by next -1; 9-11-02. 35.
Friday. © Srinivasan Seshan, 2002. L -1; 36What if the Data Doesn’t Fit? On
9-11-02. 8. Ethernet, max IP packet is 1.5kbytes
9Outline. Administrivia Whirlwind tour Typical web page is 10kbytes. Problem:
of networking. © Srinivasan Seshan, 2002. Packet size. Solution: Fragment data
L -1; 9-11-02. 9. across packets. ml. x.ht. inde. GET. GET
10What is the Objective of Networking? index.html. © Srinivasan Seshan, 2002. L
Communication between applications on -1; 9-11-02. 36.
different computers Must understand 37What if the Data is Out of Order?
application needs/demands Traffic data Problem: Out of Order. ml. inde. x.ht.
rate Traffic pattern (bursty or constant GET. GET x.htindeml. Solution: Add
bit rate) Traffic target (multipoint or Sequence Numbers. ml. 4. inde. 2. x.ht. 3.
single destination, mobile or fixed) Delay GET. 1. GET index.html. © Srinivasan
sensitivity Loss sensitivity. © Srinivasan Seshan, 2002. L -1; 9-11-02. 37.
Seshan, 2002. L -1; 9-11-02. 10. 38Network Functionality Summary. Link
11Four Steps to Networking. Multiplexing Routing Addressing/naming
Communicating across a link Connecting (locating peers) Reliability Flow control
together multiple links (internetworking) Fragmentation Etc…. © Srinivasan Seshan,
Finding and routing data to nodes on 2002. L -1; 9-11-02. 38.
internetwork Matching application 39What is Layering? Modular approach to
requirements. © Srinivasan Seshan, 2002. L network functionality Example:
-1; 9-11-02. 11. Application. Application-to-application
12A First Step. Creating a link between channels. Host-to-host connectivity. Link
nodes Link: path followed by bits Wired or hardware. © Srinivasan Seshan, 2002. L -1;
wireless Broadcast or point-to-point (or 9-11-02. 39.
both) Node: any device connected to a 40Protocols. Module in layered structure
link. © Srinivasan Seshan, 2002. L -1; Set of rules governing communication
9-11-02. 12. between network elements (applications,
13Types of Links. … Point-to-Point. hosts, routers) Protocols define:
Multiple Access. © Srinivasan Seshan, Interface to higher layers (API) Interface
2002. L -1; 9-11-02. 13. to peer Format and order of messages
14Packet Transmission Modes. Unicast Actions taken on receipt of a message. ©
Transmission to single specific receiver Srinivasan Seshan, 2002. L -1; 9-11-02.
Broadcast Transmission to all network 40.
nodes Multicast Transmission to specific 41Layering Characteristics. Each layer
subset of nodes Anycast Transmission to relies on services from layer below and
one of a specific subset of nodes. © exports services to layer above Interface
Srinivasan Seshan, 2002. L -1; 9-11-02. defines interaction Hides implementation -
14. layers can change without disturbing other
15What are Switched Networks? Switch: layers (black box). © Srinivasan Seshan,
moves bits between links Packet switching 2002. L -1; 9-11-02. 41.
Circuit switching. Switched Network. © 42Layering. User A. User B. Layering:
Srinivasan Seshan, 2002. L -1; 9-11-02. technique to simplify complex systems.
15. Application. Transport. Network. Link.
16Back in the Old Days… © Srinivasan Host. Host. © Srinivasan Seshan, 2002. L
Seshan, 2002. L -1; 9-11-02. 16. -1; 9-11-02. 42.
17Then Came TDM… Synchronous time 43Layer Encapsulation. User A. User B.
division multiplexing. Multiplex (mux). Get index.html. Connection ID.
Demultiplex (demux). © Srinivasan Seshan, Source/Destination. Link Address. ©
2002. L -1; 9-11-02. 17. Srinivasan Seshan, 2002. L -1; 9-11-02.
18TDM Logical Network View. © Srinivasan 43.
Seshan, 2002. L -1; 9-11-02. 18. 44Protocol Demultiplexing. Multiple
19Packet Switching (Internet). Packets. choices at each layer. FTP. HTTP. NV.
© Srinivasan Seshan, 2002. L -1; 9-11-02. TFTP. TCP. UDP. IPX. IP. NET1. NET2. …
19. NETn. Network. IP. TCP/UDP. Type Field.
20Packet Switching. Interleave packets Protocol Field. Port Number. © Srinivasan
from different sources Efficient: Seshan, 2002. L -1; 9-11-02. 44.
resources used on demand Statistical 45E.g.: OSI Model: 7 Protocol Layers.
multiplexing General Multiple types of Physical: how to transmit bits Data link:
applications Accommodates bursty traffic how to transmit frames Network: how to
Addition of queues. © Srinivasan Seshan, route packets Transport: how to send
2002. L -1; 9-11-02. 20. packets end2end Session: how to tie flows
21Statistical Multiplexing Gain. 1 Mbps together Presentation: byte ordering,
link; users require 0.1 Mbps when security Application: everything else. ©
transmitting; users active only 10% of the Srinivasan Seshan, 2002. L -1; 9-11-02.
time Circuit switching: can support 10 45.
users Packet switching: with 35 users, 46OSI Layers and Locations. Application.
probability that >=10 are transmitting Presentation. Session. Transport. Network.
at the same time < 0.0017. © Srinivasan Data Link. Physical. Switch. Host. Router.
Seshan, 2002. L -1; 9-11-02. 21. Host. © Srinivasan Seshan, 2002. L -1;
22Characteristics of Packet Switching. 9-11-02. 46.
Store and forward Packets are self 47Example: Transport Layer. First
contained units Can use alternate paths – end-to-end layer End-to-end state May
reordering Contention Congestion Delay. © provide reliability, flow and congestion
Srinivasan Seshan, 2002. L -1; 9-11-02. control. © Srinivasan Seshan, 2002. L -1;
22. 9-11-02. 47.
23Second Step: Internet[work]. A 48Example: Network Layer. Point-to-point
collection of interconnected networks communication Network and host addressing
Host: network endpoints (computer, PDA, Routing. © Srinivasan Seshan, 2002. L -1;
light switch, …) Router: node that 9-11-02. 48.
connects networks Internet vs. internet. 49Is Layering Harmful? Sometimes.. Layer
Internet[work]. © Srinivasan Seshan, 2002. N may duplicate lower level functionality
L -1; 9-11-02. 23. (e.g., error recovery) Layers may need
24Challenge. Many differences between same info (timestamp, MTU) Strict
networks Address formats Performance – adherence to layering may hurt
bandwidth/latency Packet size Loss performance. © Srinivasan Seshan, 2002. L
rate/pattern/handling Routing How to -1; 9-11-02. 49.
translate between various network 50Class Coverage. No coverage of
technologies. © Srinivasan Seshan, 2002. L physical and data link layer Students
-1; 9-11-02. 24. expected to know this Focus on network to
25Third Step: How To Find Nodes? application layer We will deal with:
Internet. Computer 1. Computer 2. © Protocol rules and algorithms Investigate
Srinivasan Seshan, 2002. L -1; 9-11-02. protocol trade-offs Why this way and not
25. another? © Srinivasan Seshan, 2002. L -1;
26Naming. Humans use readable host names 9-11-02. 50.
E.g. www.cmu.edu Globally unique (can 51Lecture Topics. Traditional Layering
correspond to multiple hosts) Naming Internet architecture Routing (IP)
system translates to physical address E.g. Transport (TCP) Queue management (FQ, RED)
DNS translates name to IP Address (e.g. Naming (DNS). Recent Topics Multicast Address reflects location in Mobility Active networks QOS Security
network. © Srinivasan Seshan, 2002. L -1; Network measurement Overlay networks P2P
9-11-02. 26. applications. © Srinivasan Seshan, 2002. L
27Domain Name System. It is -1; 9-11-02. 51.
Computer 1. Local DNS Server. DNS server 52Next Lecture: Design Considerations.
address manually configured into OS. How to determine split of functionality
What’s the IP address for www.cmu.edu? © Across protocol layers Across network
Srinivasan Seshan, 2002. L -1; 9-11-02. nodes Assigned Reading [Cla88] Design
27. Philosophy of the DARPA Internet Protocols
28Packet Routing/Delivery. Each network [SRC84] End-to-end Arguments in System
technology has different local delivery Design [Cla02] Tussle in Cyberspace:
methods Address resolution provides Defining Tomorrow’s Internet. © Srinivasan
delivery information within network E.g., Seshan, 2002. L -1; 9-11-02. 52.
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15-744: Computer Networking

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